Vapor sprayers



April 23,1957 H. F. BQK my 2,790,063 VAPOR sPRAzEgs H. F. BOK ET AL VAPOR SPRAYERS April 23, 1957 4 Sheets-Sheet 2 Filed Nov. 9, 1954 FIGA April 23, 1957 H. F. Box Erm.

VAPOR SPRAYERS 4 Sheets-Sheet 3 Filed NOV.. 9. 1954 FIG.

FIGJO Ain-il 23,-1957 H. F. BoK Erm.

VAPOR sPRAYERs Filed NOV. 9. 1954 4 Sheets--SheelI 4 United States Patent O VAPOR SPRAYERS Hendrik Frederik Bok, Valkenswaard, and Edward Bok, Amsterdam, Netherlands Application November 9, 1954,'Serial No. 467,867

Claims priority, application Netherlands November 10, 1953 The invention relates to a method for the spraying of a medium by means of a vapor sprayer, bringing a vapor stream into contact with a solid or liquid substance, particles whereof are to be carried along with the vapor jet. The invention further relates to vapor sprayers for the application of the method as well as to a construction of an evapora-tor chamber applicable to such vapor sprayers.

The vapor jet may be used e. g. to carry along particles from a surface to be treated, e. g. for cleaning purposes.

Other applications are the spraying of molten metal or paint by means of a vapor jet.

Until now a jet of compressed air was often used for such purposes, and the compressed air had to be obtained from liquid air containers or from compressors, which is rather cumbersome especially in smaller workshops and which is always expensive. For cleaning purposes the application of a steam jet is also Well known but this is only practical in industries where steam under high pressure is already available for other purposes, such as the driving of steam engines.

vlt is an object of the invention to provide for a simple method of obtaining a vapor jet at low cost involving an arrangement easily handled and adapted for use in small workshops.

For this purpose use is made of the fact that for many applications of a vapor sprayer the vapor of volatile liquids such as acetone, gasoline, petroleum or other hydrocarbons can be used and, by heating, a great quantity of vapor at high pressure can be obtained from a small and easily transportable quantity of such liquids.

For this purpose a quantity of such liquid is stocked in an easily transportable reservoir that is constructed as a high pressure tank and electrical heating means are provided inside this tank, so that this tank is at the same time a transportable container for the jet-medium, an evaporator for the liquid and a pressure tank. The vapor is delivered directly at high temperatures at the spraynozzle, this being a further advantage above air-jets where special heating means are to be provided for this purpose, as for many applications, such as cleaning, metaland paint-spraying, it is preferred that the jet medium is delivered at high temperatures.

Without principal changes in the construction the apparatus may be built for pressures from about to 50 or even up to 200 atmospheres, the electrical heating means being dimensioned for supply of electric energy in accordance with the maximum quantity of vapor to be delivered per time unit. Adjusting of the vapor pressure "Ice can then be obtained by adjustment of the terminal voltage at the electric heating resistance.

In air jets the medium under pressure, `as far as deliv ered by a container, is immediately available at the spray-nozzle. According to the invention the vapor has to be developed by electrical heating of the liquid stocked in the transportable reservoir which may be built in one unit with a spray pistol. f

It is an object of the invention therefore to have the vapor developed at suicient pressure Within a kfew seconds so that no disturbing retardation is met when the spraying is started or restarted at any required moment.

Forl this purpose the electric heating element is not only immersed in the liquid but there is also a direct contact between the large heating surface of the electric resistance element and the liquid. Thus advantage is taken of the fact that rnost liquids, such as hydrocarbons suited for the general purposes of spraying solid or liquid particles carried along with the vapor jet have suticient electrical insulating properties to permit the immersion of the surface of an electric heating conductor directly into the liquid.

Further, in a preferred embodiment of the liquid containing pressure tank, the electric heating resistance is enveloped by a housing provided with liquid inlet openings at its bottom and vapor outlet openings at its top so that a heating chamber for a smaller quantity of the liquid is formed within the greater Volume of the liquid container as a result, when the electric resistance isenergized a sucient development of vapor starts immediately. Further, it is an advantage that the wallsv of the pressure tank will have a much lower temperature than the heating element, which simplifies the construction of the high pressure tank and makes it easier in use.

In many cases, especially for cleaning purposes and for paint spraying, advantage is taken of the fact that a liquid to be vaporized can be chosen that is a solvent for the particles of the substance to be carried away by the vapor jet.

In paint spraying e. g. a finely divided fast drying paint coat is formed in the most advantageous way when the paint is sprayed by means of a warm jet of apaint solvent, e. g. acetone vapor. According to the invention the pressure tank is simply lled for this purpose with the volatile paint solvent (which was until now only used as a thinner to be added to the paint to make it sprayable) and the paint can be fed from a separate reservoir to the spraying pistol. In most cases the paint can be applied directly by this method in the viscous state wherein it is delivered by the dealer Without any thinner to be added to the paint before spraying.

Further objects of the invention and the .means by which they are obtained will become apparent from ,the following description taken in connection with the accompanying drawings.

Figure 1 is a vertical section of a hand sprayer for cleaning puiposes;

Figure 2 is a view of a detail thereof;

Figure 3 is a vertical section thereto;

Figure 4 is a view of a variant of this detail relating to the mounting of electrical contacts and filling opening for the tank and Figure 5 is an axial section thereto;

Figures 6 and 7 show in a Similar way respectively H in plan and in a section another variant of these partsi Figures 8 and 9 are a plan view and a section, respectively, of still another arrangement of the electric supply-contacts;

Figures 10 and ll show in a similar way another manner of mounting the electric conductors.

Figure 12 is a vertical section through `a vapor sprayer wherein the construction according to Figures -10 and ll is applied.

Figure 13 is a detail side view showing yanother arrangement of the pressure-liquid-tank with respect to the spray tube.

Figure 14 is a vertical section of a pressure tank con nected by a flexible conduit to a spray pistol.

Figure 15 shows partly in a section a metallizing gun for the application of the invention.

Figure 16 is an outline of a spraying arrangement with means to maintain the vapor at a desired temperature in the flexible conduit from the liquid tank to a spray pistol.

In Figure l the number 1 indicates a liquid reservoir being at the same time an evaporating device and a pressure tank for the vapor. rIhe tank is fully closed except for an outlet 2 for the vapor.

A plate 3 with a spray opening 4 is fixed against the outlet piece 2 by means of a cap nut 5.

An electric resistance element 6 extends inwardly from the outer wall of the tank 1 and passes through the cen- `ter thereof unto a short distance from the tank bottom. It consists of coiled resistance wire helically wound on an insulator 7, supported by a hollow metal bolt 8 the lower end 9 of which is baked into the insulator 7. One end 10 of the resistance wire is electrically connected to the supporting bolt 8 by means of a clamping screw 11.

The suspension bolt 8 is fastened into a metal plate 13 by means of the nut 12 by which a shoulder 14 of the bolt 8 is drawn against the surface of the plate 13. This plate 13 (see also Figures 2 and 3) is xed to the tank l by bolts 16, an insulating plate 15 being placed between the plate 13 and the surface of the tank 1.

The hollow suspension bolt 8 is closed at the top by a metal screw plug 17, the rounded head thereof forming a junction contact, cooperating with a contact bush 19 fastened into the wall of a cap 20 nrade of insulating material such as a thermo-hardening plastic and covering all current carrying parts on the top of the tank. The second leading in contact is formed by a pin 22 fastened into :and insulated from the plate 13 and being connected at the lower end 22 with the resistance wire 2. The head 23 of the pin 22 forms a contact plug on which the contact bush 24, fastened in the wall of the cap 20, can be applied.

The current cable 25 passes through the handle 26 of the tank and is led into the cap 20 where the current leads are connected to the contact bushes 19 and 24 respectively. By lifting the cap 20 all electrical contacts are broken and therefore the filling of the liquid through the bore of the bolt 8 after unscrewing the plug 17 takes place after the electrical tension on all parts of the tank has been taken ot.

The resistance 6 is surrounded by a cylindrical case 27 made of ceramic material and constituting a heating chamber the walls of which surround the wire 6 at a short distance.

.The lower end of the cylinder 27 is open so that the liquid can enter there and this lower end bears upon a supporting plate 28 provided on the lower end of the contact pin 22. The vapor developed in the chamber 27 can escape through the openings 29 at the top and enters into the main space of the tank 1 above the liquid level indicated by a dotted line 30. Of course this level will be higher directly after filling the tank.

As will be seen the insulator 7 bearing the resistance 6, the chamber 27 and the electric contacts are built together in one unit with the plate 13 forming a closing piece for the tank and this unit can be taken away after unscrewing the bolts 16 for cleaning purposes or replacement of parts.

In practice an apparatus as described is ready for use a few seconds after switching in the resistance as a strong development of vapor starts immediately in the small heating chamber within the cylinder 27 wherein the big surface of the resistance wire 6 is in immediate contact with the liquid to be evaporated. In a like tank bearing sprayer to be managed by hand e. g. one liter of the liquid such as gasoline or petroleum can be stored, sufficient for spraying a strong vapor jet during about l5 minutes the electric power to be supplied being about 500 watt.

For cleaning purposes when particles of hardened fat and other dirt mixed with solid particles are to be taken along in the jet from surfaces to be cleaned it may be advantageous to add warm liquid from the contents of the tank to the jet and the vapor pressure above the level 30 of the liquid in the tank may be used to introduce the liquid in the jet. In Figure l this is shown by the tube 31 indicated in dotted lines running from the bottom of the tank 1 until directly behind the spraying opening 4. The liquid is pressed by the vapor above the level 30 through the tube and into the vapor stream.

In Figures 4 and 5 a positioning of the contact pin 22, 23 `in the center of the hollow bolt 8 is shown. The upper part of the screw plug 32 forming an electric contact head is made cylindrical for this purpose and in a bore 33 of this plug a metal pin 35 is baked into an insulating ceramic mass 34. So the lead-in contacts 32 and 35 are placed concentrically and the pin 35 is not prolonged onto the lower end of the resistance 6 indicated by a dotted line but slips into :a spring contact 36 which is electrically connected with the lower end of the resistance wire 6. When unscrewing the filling plug 32 and removing it the contact plug 35 is wit'hdrawn from the spring contact 36.

In Figures 6 and 7 the tank 1 is provided with an opening 37 having an inwardly projecting edge wherein a metal bush 39 is screwed tightly by means of a shoulder 40 and a washer 41 against the wall of the tank 1. ln the bush 39 the conductors 43 and 44, having the Shape of Ia pin and a cylinder, respectively, are baked in concentrically. A second separate opening 38 in the tank wall constitutes the filling opening and it is closed by a plug that can only be removed after lifting ot' the cap 20 (shown in Idotted lines) as the cable 25 led into the cap passes over the plug 45. An extra security against removing the plug 45 when the contacts 43 and 44 are under tension can be obtained by placing a pin 47 in a bore 46 provided in the head of the plug 45, which pin can only be turned in order to unscrew the plug 45 after the cap 20 has been removed.

In the embodiment shown in Figures 8 and 9 the filling opening 48 is again combined with the opening 49 in one bung hole enabling the resistance element to be taken out of the tank 1. The bung consists of a hollow screw plug 52 in the bore whereof a central contact pin 50 and a concentric lead-in conductor 51 are baked in an insulating ceramic mass. The fastening 53 for the pin leaves however a passage 48 free for the liquid and the head of pin 50 is formed as a contact bush. The metal filling plug 55 is screwed into the head of the conductor 51 and constitutes one junction contact the second junction contact being formed by a central Contact plug 56 fitting in the bush 54 and baked in a ceramic mass 57 in the central bore of filling plug 55.

Figures l0 and 1l show how this construction is simplied for a single pole current lead in cases where the other current lead is formed by the metal mass of the tank and is grounded. The filling plug 58 is formed as a screw bung in a. bung hole 59 with an inwardly protruding edge, the bung bearing the resistance element 6 and having a bore wherein the contact pin 61 is baked in a ceramic mass 60.

Figure l2 is a section showing a'hand spraying ap` paratus wherein the sleeve 27 and resistance element mounted therein are fastened to a bung such as 52 in Figure 9 screwed into bung hole of the tank 1 with an inwardly set edge 49. The upper surface of the tank 1 is sloped and the heating chamber 27 passes through the center of the tank but with an inclination so that its lower end extends into a corner of the tank. By that positioning a part of the resistance will still be immersed in the last remaining portion of the liquid when the apparatus is used with a forward inclination the jet being directed downwardly.

Further this figure illucidates the fact that a simple and handy apparatus is obtained which can be manufactured at a low price.

From the embodiment of Figure 13 it can be seen that the tank 62 can also be suspended by means of a nipple 63 directly under a spray pistol 64 which can be provided wvith a handle or the tank 62 may be used as a handle. The spray pistol may further be provided with a separate reservoir for the material to be fed into and to be carried along by the vapor jet.

Figure 14 shows that in other circumstances e. g. when the consumption of vapo-r for spraying is so high that filling of a small tank forming part of the sprayer would become necessary at too short intervals, the pressure tank 65 wherein the liquid is to be vaporized may form a separate unit mounted on a foot 66 a flexible conduit 67 leading the vapor to a cleaning sprayer, a p-aint pistol, a mctallizing pistol or some other kind of sprayer.

In the embodiment of Figure the flexible conduit 67 is connected to the central brush 68 of a metal sprayer bearing a spraying head 69. A sleeve 70 is applied upon the bush 63 and fastened thereto by means of a shoulder 71 pressed against the end of the bush 68 by' a nut 72. Between the conical end wall 73 of the brush 68 and the tapered head 74 of the sleeve 70 an annular space is left free which opens into the spraying opening 75, the passage thereof being regulated by the thickness of the washer 76 Iunder the shoulder 71. A wire 78 of the metal to be carried along in a molten state in the vapor jet is fed into the central canal 77. This canal 77 is surrounded by an electric heating element 79 embedded between layers 80 and 81 of insulating material. The lead-in conductors for the electric current (one of them indicated by 82) are connected with the electric cable 84 in a ceramic contact-block 83 the cable 84 being led through the handle 85 of the spray pistol.

The metal wire 78 is fed from a storage roll 86 by means of a trigger 87 moving a pin 88 slidable in -a guide tube 91. On pulling the trigger 87 the pin 88 xes the wire in the casing 89, the trigger 87 then contacts the snap 90 on the guide tube 91 the latter swings on its spindle 92 and the casing 89 moves the wire 78v over a small distance on into the canal 77. On letting the trigger' 87 go the pin 88 releases the wire and the casing 89 is swung backwards sliding free over the lwire 78 under the pressure of the spring 93, so that a following feeding step may be starcd by pulling the trigger 87.

The trigger 94 is connected to a switch (not shown) housed in the handle 85 whereby at the same time the electric current for the heating element 79 and for the resistance 6 in the pressure tank 1 are switched in. In order to supply the current to the resistance 6 the cable may be connected to contact block'83.

The metal such as aluminum, cadmium, lead, tin, zinc or alloys thereof, to be carried along in the stream of vapor fed through the flexible conduit 67, is molten in the canal 77 and arrives through the canal 95 at the spraying opening 74 where it is introduced into the vapor stream.

The heat of the vapor yassists in keeping the metal on a sutlcient temperature for a. good attachment on the sur-l face to be metallized. However the vapor may also Abe burned in the head 69. The additional vapor -outlets 96 arranged in a circle around the spraying opening 75 help to bundle the medium streaming out and form a warm vapor mantle around the jet carrying the molten metal.

The parts of a spraying pistol of the kind as described are removable Aand a set of replacement pieces may be added in order to transform a metal sprayer into a paint sprayer or other sprayer.

In Figure 16 an outline is given of a pressure tank 97 for a paint sprayer 100. The hollow foot 99 contains a closing plate 98 placed in the bottom of the tank 97 on which an electric heating element 6 is mounted in a heating chamber 27. In known paint spraying methods the paint is made sprayable by adding a thinner and this mixture is put into the reservoir 112 on the top of the spray pistol 100. According to the invention however the thinner such as acetone is filled in the tank 97 and thick paint is filled in the reservoir 112. Therefore spraying can go on during a much longer time than according to the known method before the reservoir needs to be refilled, and the thinner provides for the spraying medium without necessity of an additional gas.

In the tank 97 a thermostat 102 is built in, fully immersed in the liquid when the tank is filled but emerging therefrom when the level of the liquid lowers during evaporation of the liquid as shown in the figure where the level is indicated by 101. At the time when the liquid becomes consumed the temperature in the tank increases until the resistance 6 is switched out by the thermostat.

Flfhe Vapor escapes through a feed regulating valve 103 and further a safety valve 104 is mounted on the tank. The manometer 105 indicates the pressure before and the mancmeter 106 the pressure after the valve 103. The vapor is conducted through the eXible conduit 107 to the spraying pistol 100.

The conduit 107 contains along its whole length a flexible, helically wound resistance wire 108 in order to prevent condensation of the vapor on its way to the sprayer nozzle 109. The resistance 108 may even be used as a superheater for the vapor so that it has the desired most favorable temperature when arriving in the spray jet for carrying paint in a warm condition onto the surface t-o be painted.

A switch 110 actuated by a trigger 111 of the pistol serves to switch in the current for the resistance 108.

During operation, thinner may be `fed to the tank 97 by an auxiliary arrangement indicated by dotted lines and consisting of a liquid reservoir 113 from which the liquid is pumped by the pump 115 through the suction conduit 114 and the delivery conduit 116 to the tank 97. An excess of liquid can pass through the backvalve 117 and conduit 118 back to the reservoir 113.

Having now particularly described and ascertained the nature of the invention and in what manner the same is to be performed, the following claims are made:

1. ln a method of spraying paint wherein particles of the paint are carried along by a vapor jet stream, the steps which comprise developing the vapor jet stream from a volatile thinner for the paint to be carried along by the jet in a pressure tank containing a reserve of said volatile thinner, said vapor being'developed in predetermined quantity and pressure by means of an electric resistance disposed inside the pressure tank and at least partly immersed in the thinner, and bringing said paint from a separate reservoir into contact with said jet stream.

2. A liquid container having the form of a pressure tank, said tank being adapted to contain a liquid and comprising a built-in electric resistance element for heating and evaporating the liquid in the tank, an insulator body supporting the resistance element, a hollow bolt secured in the tank wall and supporting said insulator body, said hollow bolt having a central bore and being :weones insulated from the tank wall and forming a lead-in conductor for the resistance element, the central bore of the bolt serving as a filling opening to conduct the liquid into the tank, and a plug closing said central bore, the head of said plug being formed as an outer junction contact.

3. A liquid container having the form of a pressure tank, said tank being formed with an opening and being adapted to contain ia liquid and comprising a built-1n electric resistance element for heating and evaporating the liquid in the tank by direct contact with the liquid, an insulator body supporting the resistance clement, a closure unit securable in said tank opening, said closure unit supporting said insulator body and said resistance element from its lower side, said closure unit having an axially-extending bore and a contact pin secured in said bore and insulated therefrom.

4. A liquid container having the forni et a pressure tank, said tank being formed with an opening and being adapted to contain a liquid and comprising a built-in electric resistance element for heating and evaporating the liquid in the tank by direct contact with the liquid, an insulator body supporting the resistance element, a closure unitA securable in said tank opening, said closure unit supporting said insulator body and said resistance element from its lower side, said closure unit having an axially-extending bore, a contact pin secured in said bore and insulated therefrom, the outer end of the contact pin being formed as a junction contact, and a spring contact supported by said insulator body, said spring contact engaging the inner end of said contact pin.

5. A liquid container having the form of a pressure tank, said tank being formed with an opening and being adapted to contain a liquid and comprising a builtin electric resistance element for heating and evaporating the liquid in the tank by direct contact with the liquid, an insulator body supporting the resistance element, a closure unit securable in said tank opening, said closure unit supporting said insulator body and said resistance element from its lower side, said closure unit having an axially-extending bore, a contact pin secured in said bore and insulated therefrom, the outer end of the contact pin being formed as a junction contact, a spring contact supported by said insulator body, said spring contact engaging the inner end of said contact pin, and

two insulated concentric lead-iu conductors extending f through said closure.

6. A pressure tank adapted to contain a liquid and comprising means defining a tank body having a wall, an electric resistance element extending from the tank wall into the cavity of the tank, a case closely surroundi ing said element, said case having a bottoni entrance opening for the liquid contained in the tank and a top outlet opening for vapor evolved :from said liquid, said casing defining a small heating chamber within the cavity of the tank whereby the surface of the resistance elcment is in direct contact with the liquid, a closing element for said tank connected to said case, said closing element being provided with at least one insulated leadin conductor for the electric resistance element, said leadin conductor having a junction element on the outside of said closing element, and an insulating cap adapted to overlie said closing clement, said insulating cap having counter-contact pieces adapted to engage said junction clement and being provided with an opening for reception of lan electric current supply cable, said tank being provided with a bung hole and means to prevent opening of the bung hole when the cap is in seated position in relation to the closing element.

7. A paint sprayer comprising, in combination, a spray pistol, a pressure tank and a flexible conduit connecting said pistol with said tank, said pressure tank being adapted to contain a vaporizable liquid and being provided with an electric resistance element positioned to be at least partly immersed in the liquid with the surface of the resistance element in direct contact with the. liquid, said tank `containing an evaporator chamber, a flexible resistance element disposed in the flexible conduit, and a switch common to said last-named resistance element and to the resistance element in the tank for controlling said resistance element, and a resistance element contained in the spraying pistol to heat the paint being sprayed as it is carried along in a vapor jet formed from the vapor izable liquid.

8. A vapor sprayer comprising a pressure tank adapted to contain a volatile liquid, a spraying nozzle connected to said pressure tank, an open housing suspended within said container and positioned to be immersed in said liquid, an electric resistor element mounted in said hoiing for direct contact with the volatile liquid in the tan 9. A vapor sprayer comprising a pressure tank adapted to contain a volatile liquid, a flexible conduit connected to said pressure tank, a spray gun connected to said flexible conduit, and means defining an open housing suspended within said container and positioned to be immersed in said liquid, an electric resistor element mounted in said housing for direct contact with the volatile liquid in the tank.

10. A vapor sprayer comprising a pressure tank adapted to contain a volatile liquid, a flexible conduit connected to said pressure tank, a spray gun connected to said flexible conduit, means defining a housing suspended within said container and positioned to be immersed in said liquid, an electric resistor element mounted in said housing for direct contact with the volatile liquid in the tank, means defining an inlet for the liquid in the base of the housing, and means defining a vapor outlet in the top of the housing.

1l. A vapor sprayer comprising a pressure tank adapted to contain a volatile liquid, a flexible conduit connected to said pressure tank, a spray gun connected to said flexible conduit, means defining a housing suspended in an inclined position within said container and extending from a bottom corner thereof to the opposite wall of the tank, an electric resistor element mounted in said housing for direct contact with the volatile liquid in the tank, means defining an inlet for the liquid in the base of the housing, and means defining a vapor outlet in the top of the housing.

l2. A vapor sprayer comprising a pressure tank adapted to contain a volatile liquid, a llexible conduit connected to said pressure tank, a spray gun connected to said flexible conduit, means defining a housing suspended in an inclined position within said container and extending from a bottom corner thereof to the opposite wall of the tank, an electric resistor element mounted in said housing for direct contact with the volatile liquid in the tank, means defining an inlet for the liquid in the base of the housing, means defining a vapor outlet in the top of the housing, and a flexible resistance element inserted in the flexible conduit running from the pressure tank to the spray gun.

13. A vapor sprayer comprising a pressure tank adapted to contain a volatile liquid, a flexible conduit connected to said pressure tank, a spray gun connected to said flexible conduit, means defining a housing suspended in an inclined position within said container and extending from a bottom corner thereof to the opposite wall of the tank, an electric resistor element mounted in said housing for direct contact with the volatile liquid in the tank, means defining an inlet for the liquid in the base of the housing, means defining a vapor outlet in the top of the housing, a flexible resistance element inserted in the flexible conduit extending from the pressure tank to the spray gun, and a receptacle for containing the material to be atomized connected to the spray gun.

14. A vapor device comprising a pressure tank adapted to contain a volatile liquid, a heating element mounted within said tank, said element consisting of a housing and an electric resistor element mounted in said housing,

means defining an inlet opening for the liquid in said housing, a vaporizing chamber being defined within said heating element Within which the liquid is in direct contact with the electric resistor element, and means defining a vapor outlet in said housing.

15. A vapor device comprising a pressure tank adapted to contain a volatile liquid, a heating element mounted within said tank consisting of a housing which is largely lilled with an electric resistor, means defining an inlet opening for the liquid provided in said housing, a Vaporizing chamber being defined Within said heating element within which the liquid is in direct contact With the electric resistor and means ydefining a vapor outlet provided in said housing.

References Cited in the file of this patent UNITED STATES PATENTS 1,644,081 Preble Oct. 4, 1927 1,873,820 Carpenter Aug. 23, 1932 1,905,343 Carpenter Apr. 25, 1933 2,043,002 Lechler June 2, 1936 2,291,423 Tiscornia July 28, 1942 2,481,813 Bede Sept. 13, 1949 

